JOHANNESBURG—Five fast-growing African economies lost about $15 billion in tax revenue over the past decade to companies surreptitiously moving profits abroad, research group Global Financial Integrity says in a new report.

Companies operating in Ghana, Kenya, Mozambique, Tanzania and Uganda send a total of about $3.7 billion abroad each year without alerting customs officials or paying taxes, GFI said in a report released this week. The Washington, D.C.-based research organization said that lost revenue deprives these...